This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Abdominal and pelvic surgical procedures carry a risk of accidental injury to the tissues of the renal system, and in particular, to the bladder and/or ureters. The bladder is a hollow, muscular, and elastic vesicle situated in the anterior part of the pelvic cavity. The bladder serves as a reservoir for urine until it can be eliminated from the body through the urethra. The ureters are delicate, small-diameter muscular vessels that carry urine from the kidneys to the bladder. In a healthy individual, the ureters tend to be about 25 cm to about 30 cm long and up to about 3 mm in diameter (J. W. Utrie, Bladder and Ureteral Injury, Clin. Obstet. Gynecol., 1998, 41(3):755-763; N. Zelenko et al., Normal Ureter Size on Unenhanced Helical CT, Am. J. Roentgenol. 2004, 182:1039-1041). In part because of their small diameter, the ureters are often difficult to identify in a surgical field. This is especially true in laparoscopic procedures, because the surgeon generally has a limited view of the surgical field and cannot use tactile perception to aid in identification of organs and tissues. Thus, in such procedures there is often a risk that the bladder may be unintentionally penetrated or that the ureters may be unintentionally nicked, severed, ligated, crushed, or otherwise injured.
Injuries to the bladder and ureter are not uncommon complications of hysterectomy. Hysterectomy is the second most common surgery among women in the United States, with over 600,000 such procedures performed each year (Women's Reproductive Health: Hysterectomy, http://www.cdc.gov/reproductivehealth/WomensRH/Hysterectomy.htm). Ureteral injury occurs in approximately 0.5 to 2 percent of all hysterectomies and routine gynecologic pelvic operations, and in approximately 10 percent of radical hysterectomies (S. B. Brandes, Urologic Complications from Pelvic and Vaginal Surgery: How to Diagnose and Manage, http://www.urology.wustl.edu/PatientCare/UrologicComplications.asp). Laparoscopic hysterectomy has become more popular in recent years due to its advantages over conventional surgical methods (e.g., smaller incisions, reduced hospital stays, and a speedier return to normal activities). However, laparoscopic hysterectomy generally carries a greater risk of accidental injury to the bladder and ureter as compared to conventional surgical procedures. As another example, the incidence of ureteral injury during colorectal surgery has been reported as ranging from 0.2 to 4.5% (F. Chahin, et al., The Implications of Lighted Ureteral Stenting in Laparoscopic Colectomy, JSLS, 2002, 6:49-52).
Injury to the urinary tract can result in various complications, some of which may be life-threatening. Such complications include voiding difficulties, incontinence, detrusor instability, bowel obstruction, persistent abdominal and/or flank pain, urinary tract infection, pyelonephritis, loss of kidney function that may require surgical removal of the kidney, fever/body-wide responses to serious infection, and possible death. In particular, ureteral injuries that occur during a surgical procedure are often not immediately recognized and can therefore lead to very serious complications. Such ureteral injuries may result in permanent kidney damage, possibly requiring removal of a kidney, and in some cases are life-threatening.
Methods for detecting or visualizing a ureter during abdominal or pelvic surgery generally have involved inserting a lighted catheter or stent through the urethra and bladder and into the ureter. Such methods are particularly popular in laparoscopic procedures, where tactile identification of the ureters is not possible. For example, U.S. Pat. Nos. 5,423,321, 5,517,997, 5,879,306, and 6,597,941 disclose infrared illuminated ureteral catheters coupled with infrared detection systems. Similarly, U.S. Pat. No. 5,954,652 describes a double lumen ureteral catheter device made of light transmitting material, one lumen of which houses a single fiber optic filament capable of illuminating the catheter with visible light.
Placement of a lighted ureteral catheter or stent is a highly invasive procedure. Some surgeons believe that ureteral catheters do not prevent injuries to the renal system and may in fact predispose patients to such injuries. Furthermore, placement of a lighted ureteral catheter or stent is associated with its own list of complications. For example, in one study of complications associated with placement of a lighted ureteral stent during laparoscopic colectomy, nearly all (98.4%) patients developed gross hematuria lasting approximately three days. Less frequent complications included reflux anuria which in some cases required renal support with hemodialysis for three to six days, and urinary tract infection. Placement of lighted catheters also prolonged anesthetic time by on average 26 minutes, thus increasing the cost of the procedure. Where visualization of both ureters is desired, bilateral placement of ureteral catheters may increase the likelihood and severity of these complications (F. Chahin, et al., The Implications of Lighted Ureteral Stenting in Laparoscopic Colectomy, JSLS, 2002, 6:49-52).
Because of the risk of injury to the tissues of the renal system during abdominal and pelvic surgical procedures and because of the complications associated with the placement of lighted ureteral catheters, it would be desirable to develop a non-invasive method by which a surgical patient's bladder and/or ureters can be readily visualized or detected. Furthermore, because ureteral injuries that occur during surgical procedures are often not immediately recognized and can result in very serious complications, a method facilitating immediate detection of ureteral injuries during a surgical procedure would be advantageous.
Although the majority of ureteral injuries occur in patients with no identifiable risk factors, a non-invasive method for visualization or detection of the ureters during a surgical procedure would be particularly desirable for individuals who are at increased risk for ureteral injury. For example, prolapse patients and pregnant women may have extremely dilated and thin ureters and thus are more at risk for ureteral injury. Furthermore, congenital defects in the urinary system, such as ureteral duplication, can alter the anatomy of the renal system and thus increase the likelihood of injury to the bladder and/or ureter during a surgical procedure.